When I have to do a chore or something with chemicals or dirt or anything else similar, I usually suck it up and do it. Which is terrifying. And there are times when it's just really bad and I tell her that I'm scared to. Then she just goes, "Thats just an EXCUSE. AN EXCUSE TO GET OUT OF DOING WORK!" I love my mom but... Not this particular part.
Any advice?

Hey Alex
Maybe you could talk to your school counsellor about this and let them explain stuff to your mom? Sometimes its difficult for people to understand this stuff and they don't know how to react. Counsellors are usually trained to explain all this stuff. They might be able to explain to your mom that she shouldn't ignore this and how she should handle it. She could be unsure about how to help you, how to react, hence this reaction.
I hope it works out.
Take care <3

"Words are, in my not so humble opinion, our most inexhaustible source of magic, capable of both inflicting injury and remedying it."

I would take things one step further than speaking to a school counselor. If your fear of chemicals/dirt/etc. is affecting your every day life and causing this much distress, talk to your doctor and ask for a referral to a psychological professional. There ARE forms of therapy that address these sorts of problems, such as exposure and response prevention. Rather than avoiding these situations for the rest of your life (and dealing with people who don't understand/think it's an excuse), tackle the problem head-on and make it more manageable! =) A psychological professional would also be able to educate you and your mother about this condition, whether it's OCD or a specific phobia (based on what you said, I'm not sure how this is OCD vs. a phobia of chemicals/dirt/etc.).

Something you could do in the meantime (because it may take a while to set up an appointment) is offer to do other chores to make up for it. For example, ask your mom which chore she likes the least, and offer to do that instead of work that involves being exposed to chemicals/dirt/etc. You could even offer to do extra chores around the house. Your mom may be under the impression that you're lazy or don't like to do manual labor. If you can show her that's not the case, though, then she may not give you as hard of a time.